Copepod diversity along the Congo River Basin: a first approach

peer reviewedThe free-living copepods of the Congo River Basin in Africa, the second largest in the world just after the Amazonas River Basin, are still insufficiently known because of problematic accessibility and complex logistics related to sampling. We analyzed samples from 82 sites obtained during expeditions in 2010 and 2013. The Congo River main channel and its main mouth tributaries (1700km; between Kisangani and Kinshasa), and the Kasai River and its main mouth tributaries (600km) were visited. A Schindler-Patallas trap was used in the open waters, with five samplings at each site. Twenty-five taxa were found, with dominance of immature forms (nauplii and copepodites). We recognized three undescribed species of Cyclopoida. The most speciose genera were: Microcyclops (five species), Mesocyclops, , and (three species each). The most frequent species were: Microcyclops varicans (27,6% of the samples) and Cryptocyclops sp. (10,6%). Few presumably cosmopolitan species were found, like pocyclops prasinus, , and Microcyclops varicans. Few diaptomid calanoids were found. Rarefaction and extrapolation curves revealed that the diversity found is about half that estimated considering just the open water species here studied. Spatially, the highest species richness was found in the main channel of the Congo River (23) compared to Kasai (20) and other tributaries (14, 9 from the Congo tributaries, 6 from the Kasai). The abundance of adult individuals was low, with an average of 2,36 individuals per sample when considering all water bodies. A distance-based redundancy analysis based on abundance and Bray Curtis dissimilarity index revealed two large groups of copepod species in the sites of the Congo main channel, plus two minor groups with mixed sites among Congo and Kasai main channels, and tributaries of both rivers, the latter being represented by small groups correlated with nitrogen forms, total phosphorus, and oxygen concentrations. Concerning the two large Congo´s channel groups of species, one was associated with water transparency, chlorophyll, and phytoplankton dominated by Dinophyceae, Chlorophyceae, Cryptophyceae, and diatoms. The other was correlated with conductivity, chlorophyll-a and Cyanophyceae. Kasai main channel sampling sites were dispersed among the four groups resulting from our analysis. Our results indicate that the copepod species in the area are separated into two large groups associated with black and white waters, with low and high primary productivity, respectively. The results showed a high copepod diversity along the Congo Basin as expected for large tropical rivers, and a low abundance for the adult copepods, as in other lotic environments. More species are expected to be discovered in this basin with the continuation of this investigation

Neotropical and Afrotropical freshwater copepods: recent advances

peer reviewedI present new perspectives and advances on the knowledge of free-living copepods in large tropical river basins. Currently, the greatest copepod diversity is known from the Palearctic region, with a surface about twice or thrice that of the Neotropical and Afrotropical areas, respectively. Interestingly, biological diversity estimators suggest a much higher and largely unexplored diversity in the two latter regions, potentially reaching or exceeding that of the Palearctic. I show trends for both regions, focused on Brazil and Congo Basins. Brazil comprises almost 40 % of the Neotropical region surface, including four rivers among the 20 largest in the world. Based on the literature review, there are 190 free-living copepod species in the country. Among the 12 hydrographic regions in Brazil, the richest are the Amazon and the Paraná basins, with the largest surface. Taxonomical studies on Brazilian copepods were predominant until 1979, yet, between 1980 and 1989 ecologically-oriented works were developed and became a main trend after 1990, representing over 80% of copepod studies after 2000. Molecular diversity and functional ecology are still poorly studied. Ecological studies with molecular-based diversity parameters, functional attributes or comprehensive spatialtemporal data of copepod species behavior and environmental variables have been used to detect effects of environmental changes both at population and community levels. Cyclopoid copepods composition and abundance changes according to the trophic level, but calanoids appear to be influenced by conductivity. The presence of cyanobacteria and phytoplankton of lower nutritional value can cause a bottom-up effect on the copepods, resulting in low functional diversity and increase of functional uniformity. Large filtering copepods can be replaced by small cyclopoids at increasing eutrophicated conditions. The Afrotropical region comprises four of the largest rivers worldwide. The most studied environments have been the great lakes of the rift valley (e.g. Tanganyika, Victoria, Kivu), the Nile River, and several places in South Africa. The Congo River, the second largest in the world, is almost entirely unknown in terms of copepod composition and ecology. Herein, I show initial data revealing the lack of knowledge of the l extant Congo copepod diversity, with a high potential for new species. Two expeditions made in 2013 and 2015 along the Congo and the Kasai River revealed 15 copepod species, but rarefaction and extrapolation diversity curves suggest the presence of at least double of this number. There are four large groups of copepods species in the Congo Basin, being the two largest separated by differences in primary productivity (white waters rivers) or microbial food web (black waters rivers). Copepods within the main channel of the Congo River seem to be less dissimilar than tributaries, thus reinforcing the effect of upstream basins, a trend observed in other large tropical river basins. Each large river has different copepod species especially for diaptomid calanoids and also for some Cyclopoida species, but just the last have shared species between Afrotropical and Neotropical regions. The river continuum and the flood pulse concepts were applied in these large tropical rivers, but both were disrupted by reservoirs. The large rivers of these tropical regions appear seem proportionally equal in copepod diversity according to this surface, and linked to their historical biogeography

Kajian potensi ekstrak bilberi sebagai penunjuk pH untuk memantau kesegaran makanan secara kromametri

Penunjuk pH sebagai suatu pendekatan untuk memantau kualiti atau kesegaran makanan semasa telah mendapat perhatian industri pembungkusan makanan. Penggunaan sumber semula jadi pigmen tumbuhan terutamanya daripada buah-buahan dan sayur-sayuran menjadi pilihan para pengguna untuk menggantikan pewarna sintetik dalam memastikan keselamatan makanan yang diambil setiap hari. Dalam kajian ini, ekstrak daripada bilberi telah digunakan sebagai pewarna sensitif pH. Perubahan warna sampel dikaji secara terperinci melalui kaedah kromametri dan juga kaedah spektrofotometri ultra-lembayung nampak. Warna merah terang terhasil dalam pH berasid, merah pudar pada neutral dan magenta ke kuning dalam pH beralkali. Keputusan kajian kromametri menunjukkan bahawa ekstrak bilberi berupaya mempamerkan perubahan warna yang jelas terhadap perubahan pH, iaitu terdapat perubahan nilai warna a* yang menyumbang kepada perubahan yang bererti dalam perbezaan warna keseluruhan (ΔE*). Nilai ΔE* juga ditentukan wujud hubungan linear dan kuantitatif terhadap julat pH tertentu. Oleh yang demikian, ekstrak bilberi didapati berpotensi sebagai bahan sensor untuk pH dalam membangunkan satu sensor pH bagi memantau kesegaran makanan terutamanya hasilan laut berbungkus memandangkan tahap kerosakan produk tersebut berkait rapat dengan perubahan pH ke arah alkali

Shedding light on zooplankton diversity from the Congo River Basin

peer reviewedThe Congo River Basin is the second largest in the world, and its plankton biota remains completely unknown. We studied the zooplankton diversity across 1700 km of the main channel (from the cities of Kisangani to Kinshasa) and subsequently in the mouths of the 25 largest tributaries during 2013 (N=39), and across 500 km of Kasai-Kwa River and tributaries in 2015 (N=25). We recorded 135 zooplankton species (26 for Testate Amoebae, 56 for Rotifera, 27 for Cladocera and 26 for Copepoda). At least five cladoceran and four copepod species are new. A non-metric multidimensional statistical analysis with Bray Curtis dissimilarity revealed that the zooplankton composition within Congo main channel was more similar than within the mouths of several tributaries and the Kasai-Kwa River basin. In the later, the tributaries were distinct from each other and from the main channel of Kasai River. A distance-based redundancy analysis using Bray-Curtis dissimilarity on abundance data revealed two main groups of species and limnological variables, one comprising sites with high total suspended matter, conductivity, chlorophyll, phytoplanktonabundance (white water rivers), and other with sites with high transparency and dissolved organic carbon concentration (black water rivers). Zooplankton diversity was uniform in the Congo main channel and in the Kasai-Kwa River, with low difference among sites. There was also a distinct third group, unrelated to variables. This study reveals a high diverse zooplankton community in the Congo basin, with new species and distinct community between the studied rivers, but homogeneous along each one

The feeding habit of the Cyprinidae

Rastrineobola argentea Pellegrin 1904, a small pelagic endemic cyprinid from lake Victoria was introduced into lake Bulera (Rwanda) in 1991 in order to develop a fishery. From there, it accidentally colonized lake Ruhondo. To study its biology in its new habitat, samples were collected in 2007 and size and the feeding habits of the fish were analyzed. R. argentea is smaller in lake Bulera (41.8 ± 6 mm) than in lake Ruhondo (mean total body length: 72.6 ± 15 mm). The mean total body length in lake Bulera is less than its size at the first maturity in lake Victoria (47 mm). Differences in size structure of fish between lakes Bulera and Ruhondo is attributed mainly to the food availability in the two lakes. In lake Bulera, the fish feeds on six food items with plant remnants dominant. In lake Ruhondo, R. argentea is a zooplanktivorous feeder like in lake Victoria. The dominant prey is a cladoceran species, Daphnia sp. which has not been observed in lake Bulera during the sampling period